The present invention relates generally to a display device for use in a vehicle and, more specifically, to a heads-up-display (HUD) for use in an automobile.
Distortion produced by optical properties of substrates upon which an image impinges has long been a source of concern in the imaging industry. As a result, many prior art attempts have been set forth to correct for distortion created in images due to the rendering technology employed.
U.S. Pat. No. 3,422,306 discloses a distortion correction circuit for eliminating distortion in a magnetically-deflected cathode ray tube. In pertinent part, uncorrected deflection signals are pre-distorted in an inverse manner to the distortion caused by the cathode ray tube to produce corrected deflected signals. When applied to deflection amplifiers, the corrected deflected signal causes deflection in the cathode ray tube free of pincushion and non-linearity distortions.
U.S. Pat. No. 4,658,246 discloses a system for simulating the display of visual images by a matrix of liquid crystal cells or other matrix elements and providing flexibility in selecting display characteristics such as element size, active area ratio, and signal noise content. The display employs a cathode ray tube and uses software signal processing.
U.S. Pat. No. 5,302,964 discloses a heads-up display for an aircraft that includes a digital image generator, a cathode ray tube (CRT) and an optical system that projects an image formed on the CRT screen indicating the status of the aircraft operation onto a holographic mirror combiner at a slant angle. The combiner is transparent to the pilot's direct view through the aircraft windshield, but produces a reflected image of the CRT screen that is superimposed on the direct view. Pincushion distortion in the CRT and geometric distortion caused by the slant projection angle are corrected by a digital look-up table memory that alters the initially orthogonal CRT horizontal and vertical deflection signals in a manner which is the inverse of the distortion such that the image on the combiner as viewed by the pilot appears undistorted.
U.S. Pat. No. 6,532,113 discloses display device for use in a vehicle in which an image is projected on a windshield of a vehicle so that the foreground of the vehicle and a virtual image of the image for superposition are accurately seen together even when a seat position and a physique of a driver change and when a shape of the windshield changes. A light of inverse image for superposition displayed on a display surface of a display unit in a dashboard in a vehicle is projected on a windshield so that the driver sees the foreground visible through the windshield together with a virtual image of the inverse image for superposition reflected on the windshield in front of an eye point that is a virtual image of the original image for superposition. In order to cancel out distortion arisen when the light of the inverse image for superposition is reflected on the windshield, the inverse image for superposition displayed on the display unit is distorted in advance in response to the contents stored in an external ROM provided in a control unit, which is replaceable with another ROM storing the different contents.
A need exists, therefore, to provide improved optical imaging techniques in which distortion introduced by optical properties upon which an image impinges are attenuated, if not abrogated.